The bluefin tuna is extremely valuable. One fish weighing about 340 kilograms sold for almost $400,000 in Tokyo's Tsukiji fish market in early January. But that’s just the market value—which, sadly, appears to be the only value taken into account when we consider the bluefin or any other “resource”.

The bluefin is economically valuable for a number of reasons. It’s very tasty, prized by sushi lovers the world over, especially in Japan. Sports fishers like them because they are powerful and fast and put up a good fight. Unfortunately, the main reason they are commanding such high prices is that they have become precariously rare.

The bluefin tuna is unusual. Unlike most fish, it is warm-blooded, which allows it to migrate great distances, from the cold waters off Iceland to the warm waters of the Gulf of Mexico and the Mediterranean. Their unique colouring—steely blue on top and silvery white on the bottom—camouflages them from predators above and below. They can move at speeds up to 70 kilometres an hour, thanks to their sleek shape and ability to retract their dorsal and pectoral fins. They have large appetites, satisfied by a varied diet consisting of smaller fish, crustaceans, eels, squid, and sometimes even kelp.

In the 1970s, increasing demand and prices led fishing companies to find more efficient ways to harvest bluefin. Stocks, especially of breeding-age fish, have since plummeted by more than 80 per cent over the past 40 years. The bluefin is listed by the International Union for the Conservation of Nature as “critically endangered”. Although this has led to some conservation efforts, continued legal and illegal fishing of the bluefin is pushing the fish closer to the edge. Last year, Japan led other nations to vote at the United Nations' Convention on International Trade in Endangered Species against a ban on fishing for bluefin.

And so, bluefin tuna continues to draw bidders at Tsukiji, the world’s largest fish market. In the more than two decades since my first visit there, I’ve been amazed by the decrease in average size and in abundance of species such as bluefin, and by the fact that seafood in Japan is brought to market from all over the planet.

In view of pronouncements by scientists about the imminent extinction of bluefin tuna and the possible emptying of oceans by mid-century, I recently asked some Japanese people to imagine their country without fish. “Fish are your history, your culture, your very physical makeup,” I said. But when I asked why Japan isn’t then leading the fight to protect the world’s oceans I was met by blank stares—and this from people who are environmentally aware. Globalization has allowed Japan to live on fish plundered from around the world, whereas only a century ago they lived on what their local waters contained.

One problem is the way we look at economics. There is no competing market for conservation of biodiversity—no one is willing to pay $400,000 to have fishermen leave this fish alone. Given the current demand—and prices—for bluefin tuna, it would be economically profitable to catch the very last fish. It would be worth someone’s time to fish for four years just to land a single tuna. Meanwhile, other less desirable fish stocks for which there are market substitutes tend to become unprofitable when the stocks get too low because the expense to catch them is greater than the market price.

Governments worldwide have contributed to the overexploitation of the bluefin and many other fish by subsidizing the commercial fishing industry with billions of dollars every year, much of it to build and modernize fishing vessels.

We must continue to call for a ban on fishing for bluefin and other endangered species and push for better regulation and enforcement when it comes to global fisheries. As consumers, we should also increase our awareness about seafood, and avoid eating fish that are in danger. If people in countries like Japan and China were to get serious about sustainable seafood, that would help as well. It would also be great if we could shift our thinking about economics to include the value of conservation and the services that ecosystems and plants and animals provide for us.

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